This application claims all benefits accruing under Paris Convention from the Japanese Patent Application No. 2000-370587, filed on Dec. 5, 2000.
1. Field of the Invention
The present invention relates to a relay apparatus, with reliability, which is suitable for, e.g., an application in which load as a target is driven only upon completely satisfying a plurality of input conditions for safety confirmation, etc. More particularly, the present invention relates to a relay apparatus, with a safety function by which the relay apparatus is completely operated even in a failure mode of the welding and fixing of a relay contact and an external input contact, and the failure mode is detected and is prevented at the next driving operation of the relay apparatus.
2. Description of the Related Art
The above-mentioned relay apparatus with the safety function shown in a circuit diagram in FIG. 6 is well-known. As shown in FIG. 6, the relay apparatus with the safety function comprises: two input terminals T11 and T12 and two input terminals T21 and T22, to which external non-voltage contacts are connected; two input corresponding electromagnetic relays provided corresponding to the number of the input terminals (hereinafter, one input corresponding electromagnetic relay is referred to as a first electromagnetic relay, and the other input corresponding electromagnetic relay is referred to as a second electromagnetic relay); a self-maintaining set relay for outputting a self-maintenance setting signal to the first and second electromagnetic relays; and output terminals OUT1 and OUT2 to be connected to loads.
A first switch S1 and a second switch S2 connected to the input terminals T11 and T12 and the input terminals T21 and T22 comprise contacts such as limit switches comprising external non-voltage contacts. A coil K1 of the first electromagnetic relay functions as an input corresponding electromagnetic relay, a coil K2 of the second electromagnetic relay functions as an input corresponding electromagnetic relay, and a coil K3 of a third electromagnetic relay functions as a self-maintaining relay.
The coil K1, a constant-opened contact K1-2 for output, a constant-opened contact K1-1 for control, and a constant-closed contact K1-3 for control are provided for the first electromagnetic relay which functions as the input corresponding electromagnetic relay. Also, the coil K2, a constant-opened contact K2-2 for output, a constant-opened contact K2-1 for control, and a constant-closed contact K2-3 for control are provided for the second electromagnetic relay which functions as the input corresponding electromagnetic relay. Further, constant-opened contacts K3-1 and K3-2 for outputting a self-maintenance setting signal to the first electromagnetic relay and the second electromagnetic relay and a constant-closed contact K3-3 for output are provided for the third electromagnetic relay which functions as the self-maintaining relay.
The first switch S1 connected to the input terminals T11 and T12, as the external non-voltage contact, the constant-opened contact K1-1 for control of the first electromagnetic relay, as the input corresponding electromagnetic relay assigned to the first switch S1, and the coil K1 of the first electromagnetic relay are serially connected among terminals of a power source E. As a consequence, a self-maintaining circuit of the first electromagnetic relay is formed in which the first switch S1 is a contact for reset and the constant-opened contact K1-1 for control is a contact for maintenance.
Also, the second switch S2 connected to the input terminals T21 and T22, as the external non-voltage contact, the constant-opened contact K2-1 for control of the second electromagnetic relay, as the input corresponding electromagnetic relay assigned to the second switch S2, and the coil K2 of the second electromagnetic relay are serially connected among terminals of the power source E. As a consequence, a self-maintaining circuit of the second electromagnetic relay is formed in which the second switch S2 is a contact for reset and the constant-opened contact K2-1 for control is a contact for maintenance.
The constant-closed contacts K1-3 and K2-3 for control of the first and second electromagnetic relays as the input corresponding electromagnetic relays are serially connected and are inserted to a closed circuit via the power source E. The coil (input circuit) K3 of the third electromagnetic relay comprising the self-maintaining relay is further inserted to the closed circuit. The above-mentioned switch for set in the self-maintenance comprises the constant-opened contacts (output circuits) K3-1 and K3-2 for control of the third electromagnetic relay comprising the self-maintaining relay.
Further, the constant-opened contacts K1-2 and K2-2 of the first and second electromagnetic relays as the input corresponding electromagnetic relays and the constant-closed contacts K3-3 for output of the third electromagnetic relay as the self-maintaining relay are serially connected between the output terminals OUT1 and OUT2. As a consequence, a closed circuit via a load (not shown) is constituted.
Next, an operation will be described. When all of the first electromagnetic relay, the second electromagnetic relay, and the third electromagnetic relay are normal, only if both the first switch S1 and the second switch S2 are closed, an interval between the output terminal OUT1 and the output terminal OUT2 is opened. In other words, if one of the first switch S1 and the second switch S2 is opened, the interval between the output terminal OUT1 and the output terminal OUT2 is opened.
If a failure of contact welding (fixing) is caused in any of the first electromagnetic relay, the second electromagnetic relay, and the third electromagnetic relay, even if the failed electromagnetic relay is operated, one of the first switch S1 and the second switch S2 is opened. The interval between the output terminal OUT1 and the output terminal OUT2 is normally opened. Further, when a failure of devices is caused in the relay apparatus with the safety function, even if both the first switch S1 and the second switch S2 are thereafter closed, the interval between the output terminal OUT1 and the output terminal OUT2 is not closed. That is, if a failure is caused at the coil or the contact of the incorporated relay, the safety function is automatically operated.
However, the conventional relay apparatus needs a single electromagnetic relay as a self-maintaining relay as well as the two electromagnetic relays as the input corresponding electromagnetic relays and, therefore, there is a problem in that the overall apparatus is necessarily increased in scale.
The present invention is devised in the consideration of the above-mentioned problem and it is an object of the present invention to provide a relay apparatus, with a safety function, which is miniaturized.
To accomplish the above-mentioned object, according to the present invention, there is provided a relay apparatus comprising: at least one self-maintaining relay and another self-maintaining relay which are provided corresponding to input terminals; a dielectric which charges and discharges electrical energy; energizing means which energizes the dielectric and charges the electrical energy to the dielectric; one starting means which outputs a start signal to an input side of the one self-maintaining relay and enables a self-maintaining circuit of the one self-maintaining relay to be formed; another starting means which is operated by a self-maintaining operation of the one self-maintaining relay, outputs the electrical energy charged to the dielectric as a start signal, and enables a self-maintaining circuit of the other self-maintaining relay to be formed; and output means which is operated by the self-maintaining operations of the one self-maintaining relay and the other self-maintaining relay and outputs an output signal to an output terminal connected to a load, and wherein the one self-maintaining relay and the other self-maintaining relay comprise an electromagnetic relay and the other starting means comprises an electronic circuit including the dielectric.
With the above-mentioned structure, the energizing means charges the electrical energy to the dielectric. The one starting means outputs the start signal to the input side of the one self-maintaining relay and enables the self-maintaining circuit of the one self-maintaining relay to be formed. The other starting means is operated by the self-maintaining operation of the one self-maintaining relay, outputs the electrical energy charged to the dielectric as the start signal, and enables the self-maintaining circuit of the other self-maintaining relay to be formed. An interval between output terminals in the output means is energized and the load connected to the energized interval can be driven.
In this case, the one self-maintaining relay and the other self-maintaining relay comprise the electromagnetic relay, and the other starting means comprises the electronic circuit including the dielectric. The relay apparatus can be miniaturized with the safety function and with low costs.
If a failure due to short-circuit is caused in the one starting means, the energizing means charges the electrical energy to the dielectric. However, since the one starting means is failed due to the short-circuit, the self-maintaining circuit of the one self-maintaining relay is formed and the dielectric cannot sufficiently be charged.
By self-maintaining the one self-maintaining relay, the other starting means is operated. However, since the dielectric cannot sufficiently be charged, the self-maintaining circuit of the other self-maintaining relay is not formed. The interval between the output terminals in the output means is not energized and the load cannot be driven.
As mentioned above, by driving no load, not only the safety function can further be improved but also the occurrence of the failure due to the short-circuit can easily and fast be detected.
In the relay apparatus according to the present invention, the one self-maintaining relay and the other self-maintaining relay comprise an electromagnetic relay with a forced guiding mechanism, and the other starting means comprises: the dielectric which charges the electrical energy by energization and discharges the electrical energy when the other self-maintaining relay is self-maintained; switching means for start, which outputs a start signal to the other self-maintaining relay; first switching means which is operated when the one self-maintaining relay is self-maintained and outputs the electrical energy charged to the dielectric, as the start signal; and second switching means which is operated by receiving the output signal from the first switching means and conducts a power voltage to the switching means for start so as to operate the switching means for start.
The switching means for start is a transistor for start. The first switching means comprises a first photo coupler. The first photo coupler comprises a light-emitting diode which emits light as an output when the one self-maintaining relay is self-maintained and a light-receiving transistor which is operated by the output of the light-emitting diode and outputs the electrical energy charged to the dielectric as the start signal, and the second switching means comprises a second photo coupler, the second photo coupler comprises a light-emitting diode which emits light as an output by receiving the output signal of the light-receiving transistor in the first photo coupler and a light-receiving transistor which is operated by the output of the light-emitting diode and conducts the power voltage to the transistor for start so as to operate the transistor for start.
Therefore, the energizing means charges the electrical energy to the dielectric, the first switching means is operated when the one self-maintaining relay is self-maintained, and the electrical energy charged to the dielectric is outputted, as the start signal. The second switching means is operated by the start signal and the power voltage is conducted to the switching means for start (transistor for start) so as to operate the switching means for start (transistor for start). The other self-maintaining relay is self-maintained, thus, the interval between the output terminals is energized, and the load connected to the energized interval can be driven.
In this case, the one self-maintaining relay and the other self-maintaining relay comprise the electromagnetic relay with the safety function, and the other starting means comprises the electronic circuit. Therefore, the relay apparatus can be miniaturized with the safety function and with low costs.
If a failure due to short-circuit is caused in the one starting means, the other starting means is operated by self-maintaining the one self-maintaining relay. However, since the electrical energy cannot sufficiently be charged to the dielectric, the self-maintaining circuit of the other self-maintaining relay is not formed. The interval between the output terminals in the output means is not energized and the load is not driven. By driving no load, not only the safety function can further be improved but also the occurrence of failure due to the short-circuit can easily and fast be detected.
In the relay apparatus according to the present invention, the one self-maintaining relay and the other self-maintaining relay comprise an electromagnetic relay with a forced guiding mechanism, the other starting means comprises: the dielectric which charges the electrical energy by energization and discharges the electrical energy when the other self-maintaining relay is self-maintained; third switching means which is operated when the one self-maintaining relay is self-maintained and outputs the electrical energy charged to the dielectric, as the start signal; and fourth switching means which is operated by receiving the start signal from the third switching means and conducts a power voltage to an input side of the other self-maintaining relay so as to self-maintain the other self-maintaining relay.
The third switching means comprises a third photo coupler, the third photo coupler comprises a light-emitting diode which emits light as an output when the one self-maintaining relay is self-maintained and a light-receiving transistor which outputs the electrical energy charged to the dielectric as the start signal, and the fourth switching means comprises a fourth photo coupler, the fourth photo coupler comprises a light-emitting diode which emits light as an output by receiving the output signal of the light-receiving transistor in the third photo coupler and a light-receiving transistor which is operated by the output of the light-emitting diode and conducts the power voltage to an input side of the other self-maintaining relay so as to self-maintain the other self-maintaining relay.
Therefore, the energizing means charges the electrical energy to the dielectric, the third switching means is operated when the one self-maintaining relay is self-maintained, and the electrical energy charged to the dielectric is outputted, as the start signal. The fourth switching means is operated by the start signal and a power voltage is conducted to the input side of the other self-maintaining relay so as to self-maintain the other self-maintaining relay. Thus, the interval between the output terminals is energized and the load connected to the energized interval can be driven.
In this case, the one self-maintaining relay and the other self-maintaining relay comprise the electromagnetic relay with a forced guiding mechanism, and the other starting means comprises the electronic circuit. Accordingly, the relay apparatus can be miniaturized with the safety function and with low costs.
If a failure due to short-circuit is caused in the one starting means, the other starting means is operated by self-maintaining the one self-maintaining relay. However, since the electrical energy cannot sufficiently be charged to the dielectric, the self-maintaining circuit of the other self-maintaining relay is not formed. The interval between the output terminals is not energized and the load is not driven. By driving no load, not only the safety function can further be improved but also the occurrence of failure due to the short-circuit can easily and fast be detected.
In the relay apparatus according to the present invention, the one self-maintaining relay and the other self-maintaining relay comprise an electromagnetic relay with a forced guiding mechanism, and the other starting means comprises: the dielectric which charges the electrical energy by energization and discharges the electrical energy when the one self-maintaining relay is self-maintained; switching means for start, which outputs the start signal to the other self-maintaining relay; and fifth switching means which is operated when the one self-maintaining relay is self-maintained and conducts the electrical energy charged to the dielectric to the switching means for start so as to operate the switching means for start.
The switching means for start is a transistor for start. The fifth switching means comprises a fifth photo coupler. The fifth photo coupler comprises a light-emitting diode which emits light as an output when the one self-maintaining relay is self-maintained and a light-receiving transistor which is operated by the output of the light-emitting diode and conducts the electrical energy charged to the dielectric, as the start signal, so as to operate the transistor for start.
Therefore, the energizing means charges the electrical energy to the dielectric. The fifth switching means is operated when the one self-maintaining relay is self-maintained, and conducts the electrical energy charged to the dielectric to the switching means for start so as to operate the switching means for start (transistor for start). The self-maintaining relay is self-maintained. Thus, the interval between the output terminals is energized and the load connected to the energized interval can be driven.
In this case, the one self-maintaining relay and the other self-maintaining relay comprise the electromagnetic relay with a forced guiding mechanism, and the other starting means comprises the electronic circuit. Accordingly, the relay apparatus can be miniaturized with the safety function and with low costs.
If a failure due to short-circuit is caused in the one starting means, the other starting means is operated by self-maintaining the one self-maintaining relay. However, since the electrical energy cannot sufficiently be charged to the dielectric, the self-maintaining circuit of the other self-maintaining relay is not formed. The interval between the output terminals in the output means is not energized and the load is not driven. By driving no load, not only the safety function can further be improved but also the occurrence of failure due to the short-circuit can easily and fast be detected.
In the relay apparatus according to the present invention, the energizing means is an external input contact portion which outputs a self-maintenance setting signal to the one self-maintaining relay, the one starting means is an external input contact portion for start, which outputs a self-maintenance setting signal to the one self-maintaining relay.
The relay apparatus according to the present invention further comprises: threshold setting means which sets a threshold of a drive voltage for driving the transistor for start.
The relay apparatus according to the present invention further comprises: threshold setting means which sets a threshold of a drive voltage for driving the light-receiving transistor in the fourth photo coupler.
The threshold setting means comprises: the dielectric which varies a charge voltage by changing a capacitance; a resistor which limits charges in the dielectric; and a Zener diode for setting a threshold, which outputs the drive voltage when the charge voltage of the dielectric is higher than a set voltage.
With the above-mentioned structure, the threshold can be determined depending on the selection of the resistor, the Zener diode for setting the threshold, and the dielectric. Further, since the failure due to the short-circuit in the external input for start can be solved in response to the user""s request, a relay apparatus having two systems can be realized on a single substrate without changing the circuit structure.
Incidentally, in the xe2x80x9celectromagnetic relay with the forced guiding mechanismxe2x80x9d including one electromagnetic relay and another electromagnetic relay, when a constant-opened contact of the one electromagnetic relay is welded (fixed), a constant-closed contact of the other electromagnetic relay is opened while the coil is not excited and, further, when a constant-closed contact of the one electromagnetic relay is welded (fixed), a constant-opened contact of the other electromagnetic relay is opened while the coil is excited.